The use of inhalation devices in the administration of medicaments, for example in bronchodilation therapy is well known. Such devices generally comprise a body or housing within which a medicament carrier is located. Known inhalation devices include those in which the medicament carrier is a blister pack containing a number of blister pockets for containment of medicament in dry powder form. Such devices typically contain a mechanism for accessing a medicament dose by opening one or more blister pockets. The mechanism for example, comprises either piercing means or peeling means to peel a lid sheet away from a base sheet of the blister pack. The powdered medicament is then liberated from the opened blister pocket(s) for inhaled delivery to the patient.
Inhalation devices of the type described above comprise an element, generally referred to as a manifold, for guiding airflow towards one or more opened blister pocket(s) for liberating the powder contained therein; and subsequently guiding that liberated powder to a mouthpiece for inhalation by a patient. It is appreciated that the characteristics of the manifold are important in both ensuring effective liberation of powder and in subsequently guiding that liberated powder to the mouthpiece.
It is now appreciated that the form of the manifold can affect the particle size characteristics of the liberated medicament powder, which characteristics are known to be pharmaceutically important. In particular, it is now appreciated that fine particle fraction can be influenced by the form of the manifold. As known in the art, “fine particle fraction” or FP Fraction generally refers to the percentage of particles within a given dose of aerosolised medicament that is of “respirable” size. It is desirable that the form of the manifold acts such as to increase the FP Fraction of the liberated powder that is made available at the mouthpiece for inhalation by the patient.
It is further appreciated that manifold performance (e.g. FP fraction of dispensed medicament powder) can be influenced by the arrangement of a chamber through which the liberated medicament powder is transported (i.e. entrained within an airflow) to be made available at the mouthpiece. More particularly, it is now appreciated that it is beneficial that the chamber is arranged to promote break up (e.g. de-aggregation or de-agglomeration) of the liberated medicament powder that is transported there through.
In accordance with one aspect of the present invention, the manifold is provided with both a chimney with a chimney inlet and chimney exit; and a chamber with a chamber inlet and a chamber exit. In use, all airflow into the manifold is via the chimney inlet. The chimney exit and chamber inlet lie side-by-side each other such that when a medicament powder-containing, open blister pocket of a blister pack is positioned adjacent thereto at least a portion of that airflow can be directed from the chimney exit to the chamber inlet via the open blister pocket to entrain said medicament powder and enable transport thereof in the airflow from the chamber inlet to the chamber outlet. To promote break up of that medicament powder, one or more bleed holes are provided between the chimney and the chamber such that bleed airflow may be directed into the chamber to disruptively impact the airflow that transports the entrained medicament powder.
It may thus be appreciated that, in use, the total airflow entering the chimney of the manifold is ‘separated’ into that portion which is directed at the open blister pocket to entrain the medicament powder and that portion which is directed through the one or more bleed holes as bleed air. One advantage of the present manifold is that it may be fine tuned to determine the percentage of total airflow that constitutes each of these ‘separated’ portions and to thereby, allow for fine tuning of manifold performance.
Prior art manifolds (including those described by earlier patent publications WO98/30262, WO98/11929, WO 02/102,444, U.S. Pat. Nos. 2,587,215, 5,383,850, EP-A-1,106,196, WO 94/08552, WO 94/11044, U.S. Pat. Nos. 5,590,645 and 5,113,855) have been described to comprise bleed holes to a chamber or mouthpiece element. These prior art manifolds are designed, in use, to draw bleed air through an air inlet which communicates directly with the external environment (i.e. directly with the outside air).